Applications of electron spin resonance in the analytical chemistry of transition metal ions: Part I. Factors affecting the signal amplitude

An evaluation of the effect of modulation amplitude (M) and microwave power (P) on the peak-to-peak amplitude (A) of the first derivative e.s.r. signal of each of Mn²⁺, VO²⁺ and Cu²⁺ is described. It is shown that A is not directly proportional to M over all values of M and therefore for optimal precision of measurement, M should be kept constant. A varies with P^k, where k is a constant for a particular metal ion-solvent system. Limits of detection and concentration ranges of analytical utility are also reported.